The present invention relates to a hydrodynamic torque converter comprising bridging means permitting the slip-free coupling of the input and output shafts of the converter.
A hydrodynamic torque converter of this general type may advantageously be used in an automatic transmission for motor vehicle which provides several gear or drive ratios, the change from one ratio to another occuring during the torque transmission. In a transmission of this character, the hydrokinetic torque converter is disposed between the power unit and the change-speed mechanism. The function of the torque converter is to multiply the input torque delivered by the vehicle engine by a certain coefficient during a transient phase also referred to as the torque conversion phase. Beyond a predetermined value of the rotational speed of the output shaft of this converter, the torque conversion phase comes to an end and a coupling phase begins during which, however, a certain degree of slip takes place between the input and output members of the converter, and reduces the total efficiency of the power unit and transmission assembly while increasing the fuel consumption. In order to reduce the engine fuel consumption in a vehicle having an automatic transmission with torque converter, various means have already been proposed for rigidly coupling the input and output members right at the end of the conversion phase in order to eliminate any detrimental slip. This constitutes the so-called "bridging" between the output shaft and the input shaft of the torque converter.
Among the known devices developed for controlling the bridging of torque converters, a few comprise external hydraulic-fluid supply means separate from the circuit for feeding or overfeeding the converter inner space. This leads to a considerable intricacy of the bridge control system and also to the impossibility of constructing a compact device.